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Junctional ectopic tachycardia (JET) complicates congenital heart surgery in 2% to 8.3% of cases. JET is associated with postoperative morbidity in single-center studies. We used the Pediatric Cardiac Critical Care Consortium data registry to provide a multicenter epidemiologic description of treated JET. This is a retrospective study (February 2019-August 2022) of patients with treated JET. Inclusion criteria were (1) <12 months old at the index operation, and (2) treated for JET <72 hours after surgery. Diagnosis was defined by receiving treatment (pacing, cooling, and medications). A multilevel logistic regression analysis with hospital random effect identified JET risk factors. Impact of JET on outcomes was estimated by margins/attributable risk analysis using previous risk-adjustment models. Among 24,073 patients from 63 centers, 1436 (6.0%) were treated for JET with significant center variability (0% to 17.9%). Median time to onset was 3.4 hours, with 34% present on admission. Median duration was 2 days (interquartile range, 1-4 days). Tetralogy of Fallot, atrioventricular canal, and ventricular septal defect repair represented >50% of JET. Patient characteristics independently associated with JET included neonatal age, Asian race, cardiopulmonary bypass time, open sternum, and early postoperative inotropic agents. JET was associated with increased risk-adjusted durations of mechanical ventilation (incidence rate ratio, 1.6; 95% CI, 1.5-1.7) and intensive care unit length of stay (incidence rate ratio, 1.3; 95% CI, 1.2-1.3), but not mortality. JET is treated in 6% of patients with substantial center variability. JET contributes to increased use of postoperative resources. High center variability warrants further study to identify potential modifiable factors that could serve as targets for improvement efforts to ameliorate deleterious outcomes. [ABSTRACT FROM AUTHOR]

The flow field design is very essential to the material distribution uniformity and overall output performance of planar solid oxide fuel cells. In this paper, the structure of the external manifold and cathode side interconnect is optimized to solve the uneven flow field distribution problem. The effects of crucial geometric parameters on the internal mass transfer, component transport, electrochemical reaction, temperature field and overall output performance of the fuel cell are studied by three-dimensional multi-physics numerical simulation. It is found that the combination of the three-inlet-two-outlet external manifold and cylindrical ribbed interconnect significantly reduces the uneven gas distribution between different channels and greatly improves the diffusion of oxygen under the ribs, thus enhancing the overall output performance of SOFC. Increasing the number of cylindrical ribs is beneficial to the transport and uniform distribution of oxygen. However, the excessive number of cylindrical ribs will hinder oxygen diffusion to the end of the flow channel, resulting in increased concentration polarization along the flow channel. Moreover, reducing the total contact area of the ribs enhances oxygen diffusion beneath the ribs but also raises the contact resistance and may deteriorate the cell performance. • The structure of external manifold and cathode side interconnect is optimized. • The discrete cylindrical ribs significantly enhance the diffusion of oxygen beneath the ribs. • An excessive quantity of cylindrical ribs hinder the flow of oxygen to the end of the channel. • Reducing the contact area of the ribs leads to a rise in ASR and performance degradation. [ABSTRACT FROM AUTHOR]

Safely minimizing postoperative mechanical ventilation duration after congenital heart surgery could be a cardiac intensive care unit (CICU) quality measure. We aimed to measure CICU performance using duration of postoperative mechanical ventilation and identify organizational factors associated with this metric. Observational analysis of 16,848 surgical hospitalizations of patients invasively ventilated on admission from the operating room from 26 Pediatric Cardiac Critical Care Consortium CICUs. We fitted a multivariable model to predict duration of postoperative mechanical ventilation adjusting for pre- and postoperative factors to measure CICU performance accounting for postoperative illness severity. We used our model to calculate observed-to-expected (adjusted) ventilation duration ratios for each CICU, describe variation across CICUs, and characterize outliers based on bias-corrected bootstrap 95% CIs. We explored associations between organizational characteristics and patient-level adjusted ventilation duration by adding these as independent variables to the model. We observed wide variation across CICUs in adjusted ventilation duration ratios, ranging from 0.7 to 1.7. Nine of 26 CICUs had statistically better than expected ventilation duration, while 10 were significantly worse than expected. Organizational characteristics associated with shorter adjusted ventilation duration included mixed (60%-90%) staffing by critical care or anesthesia-trained attendings, lower average attending-to-patient ratio, average CICU daily occupancy 80% to 90%, and greater nurse staffing ratios and experience. CICU performance in postoperative duration of mechanical ventilation varies widely across Pediatric Cardiac Critical Care Consortium centers. Several potentially modifiable organizational factors are associated with this metric. Taken together, these findings could spur efforts to improve ventilation duration at outlier hospitals. [ABSTRACT FROM AUTHOR]

The effects of height, length and angle of obstacle in the flow channel on the performance of solid oxide fuel cell (SOFC) are studied by computational fluid dynamics (CFD). The results show increasing the height of the obstacle can improve the cell performance, but the optimization effect is not significant when the height of the obstacle is too low. As the length of the obstacle increases, the cell performance gradually increases. But too long length will reduce the improvement of cell performance and eventually lead to performance degradation. As the obstacle angle increases, the cell performance also increases. The geometric parameters affecting the cell performance from large to small are height, angle and length. The power density of the cell with the optimal obstacle length, height and angle of 2.4 mm, 0.6 mm and 135° is 17% higher than that of the cell with the traditional rectangular channel. • The geometric parameters of obstacle channel's height, length and angle are studied. • The influence on cell performance from large to small is height, angle and length. • The optimization of obstacles channel structure greatly improve the cell performance. • The obstacles channel reduces the temperature gradient of the cell. [ABSTRACT FROM AUTHOR]

This study analyzed the influence of channel resistance, inlet flow rate, manifold depth and other related parameters on the gas distribution uniformity and pressure drop in an external 20-cell solid oxide fuel cell stack by computational fluid dynamics (CFD) technique. It provides a basis for determining the physical and geometric parameters of the stack. Furthermore, the flared inlet tube structure shows the effect of controlling the initial velocity of gas inflow and buffering; the flared outlet tube structure has the benefit of reducing the local pressure loss and the pressure drop. Combined with the perforated sheet structure, the gas in the inlet manifold is redistributed to improve the uniformity of gas flow. Compared with the basic model, the pressure drop of perforated sheet stack was reduced by 17.6% from 349.5 Pa to 288.5 Pa, and the gas flow uniformity index of that was reduced from 4.06% to 0.22%. • The physical and geometric parameters of a 20-cell SOFC stack are studied. • The diameter of inlet and outlet flared tubes are optimized. • A perforated sheet is designed to improve the flow uniformity and pressure drop. [ABSTRACT FROM AUTHOR]

The Norwood operation is a complex neonatal surgery. There are limited data to inform the timing of sternal closure. After the Norwood operation, delayed sternal closure (DSC) is frequent. We aimed to examine the association of DSC with outcomes, with a particular interest in how sternal closure at the time of surgery compared with the timing of DSC. Our outcomes included mortality, length of ventilation, length of stay, and postoperative complications. This retrospective study included neonates who underwent a Norwood operation reported in the Pediatric Cardiac Critical Care Consortium registry from February 2019 through April 2021. Outcomes of patients with closed sternum were compared to those with sternal closure prior to postoperative day 3 (early closure) and prior to postoperative day 6 (intermediate closure). The incidence of DSC was 74% (500 of 674). The median duration of open sternum was 4 days (interquartile range 3-5 days). Comparing patients with closed sternum to patients with early sternal closure, there was no statistical difference in mortality rate (1.1% vs 0%) and the median hospital postoperative stay (30 days vs 31 days). Compared with closed sternum, patients with intermediate sternal closure required longer mechanical ventilation (5.9 days vs 3.9 days) and fewer subsequent sternotomies (3% vs 7.5%). For important outcomes following the Norwood operation there is no advantage to chest closure at the time of surgery if the chest can be closed prior to postoperative day 3. [ABSTRACT FROM AUTHOR]

Acute pancreatitis (AP) is increasingly recognized as a risk factor for diabetes mellitus (DM). We aimed to study the association of pancreatitis genes with pancreatic endocrine insufficiency (pre-DM and DM) development post-AP in children. This was an observational cohort study that enrolled subjects ≤21 years with their first episode of AP and followed them for 12 months for the development of pancreatic endocrine insufficiency. Pancreatitis risk genes (CASR , CEL , CFTR , CLDN2 , CPA1 , CTRC , PRSS1 , SBDS , SPINK1 , and UBR1) were sequenced. A genetic risk score was derived from all genes with univariable P <.15. A total 120 subjects with AP were genotyped. Sixty-three subjects (52.5%) had at least 1 reportable variant identified. For modeling the development of pancreatic endocrine insufficiency at 1 year, 6 were excluded (2 with DM at baseline, 3 with total pancreatectomy, and 1 death). From this group of 114, 95 remained normoglycemic and 19 (17%) developed endocrine insufficiency (4 DM, 15 pre-DM). Severe AP (58% vs 20%; P =.001) and at least 1 gene affected (79% vs 47%; P =.01) were enriched among the endocrine-insufficient group. Those with versus without endocrine insufficiency were similar in age, sex, race, ethnicity, body mass index, and AP recurrence. A model for pre-DM/DM development included AP severity (odds ratio, 5.17 [1.66–16.15]; P =.005) and genetic risk score (odds ratio, 4.89 [1.83–13.08]; P =.002) and had an area under the curve of 0.74. In this cohort of children with AP, pancreatitis risk genes and AP disease severity were associated with pre-DM or DM development post-AP. [ABSTRACT FROM AUTHOR]